GUITAR STRINGS STRUCTURE
Both the sound and the feel of a guitar or bass string is strongly influenced
by the material and the way the strings itself is built.
While an acoustic guitar string doesn't need any particular magnetic property and it's usually covered with bronze a highly resonant material
(the same bells are made of),
bass or guitar strings are made of an internal most of the times hexagonal steel core
around which, highly precise CNC machinery wrap different wires of
steel or nickel plated
The way and the number the wraps are wounded around the core, the section and size of the core, the tension of the wrapping, all this
will strongly influence the tone, resistance and the hardness of the string.
The harder the material used the more the brightness and the rough feel on the finger tips and the more fret wear a string will deliver.
There are at least 3 different types of winding used for guitar and bass strings:
The difference in the above types of strings consists in the profile (section) of the external winding.
WHAT MAKES A STRING HARDER OR LESS?
As we increase the diameter of a plain string it becomes harder and less flexible. This is why we will never find a wound guitar B string. The maximum will be a G one. An unwound D string would not vibrate properly (too rigid) and would give us the impression to play a steel bar.
At the increase of the diameter and lowering of the note pitch, corresponds the reduction of the internal diameter core and the introduction of external windings.
External windings give us the possibility to increase the diameter, achieve a lower tone still maintaining good flexibility and added brightness. As I said previously, a wound string is made of a internal core over which are wrapped a number of windings.
The result is that it is possible to modify the strings stiffness by varying the internal core diameter and even its section shape (round or hexagonal).
An hexagonal internal core section allows the same diameter of a round one but with less material i.e. more flexibility.
The hexagonal section also adds brightness to the tone due to the empty space between the core itself and the external windings.
Same will happen achieving the same gauge by reducing the internal core diameter in favour of the external winding diameter. More brightness is added.
This is why round wound strings are brighter and flat wound sound darker.
On the other side a major internal diameter and a reduced external windings diameter will increase stiffness and therefore sustain, volume and durability.
Taking advantage of all the above, by raising the internal diameter of the core and reducing the external windings one, Galli an italian strings manufacturer, was was able to recently build a series of strings which for the same diameter is more rigid and is therefore more usable for drop tunings players who need lower notes at reduced gauges.
TYPES AND MATERIALS
The different materials used to build the different types of strings, will sound different but will also have a different impact on the strings feel under you fingertips when playing.
Many of the modern guitar players techniques require lower notes on the instrument and this can only be achieve by adding strings on the bass side which are usually too big or too loose which cause problems in playing (touch must be soft where attack and force is required instead) and buzz on the fretboard.
This problem could be achieved by modifying the inner structure of the string.
By increasing the inner core diameter and reducing the outer winding coils diameter we will achieve a stiffer strings sounding deeper and still retaining an adequate stiffness which allows "drop-tunings" without buzz.